Hybrid spring
A complex spring unit ( 10 ) comprises at least a first spring portion ( 12 ) and a second spring portion ( 14 ), which first and second spring portions are integrally formed, wherein the first spring portion is arranged in use to be placed under compression, and the second spring portion is arranged in use to be placed under tension, during compression of the complex spring unit.
1. A complex spring unit including first and second opposed ends, the unit comprising at least first and second co-axial coil spring portions integrally formed from coiled wire, wherein the first spring portion is helical and is arranged in use to be placed under compression during compression of the complex spring unit, and the second spring portion comprises a plurality of coils of differing diameters and is axially spaced from the first and second ends and arranged in use to be placed under tension during compression of the complex spring unit.
2. A complex spring unit according to claim 1 , wherein the complex spring unit comprises a third integrally formed spring portion, which third spring portion is arranged in use to be placed under compression during compression of the complex spring unit.
3. A complex spring unit according to claim 2 , wherein the complex spring unit comprises a fourth integrally formed spring portion, which fourth spring portion is arranged in use to be placed under tension during compression of the complex spring unit.
4. A complex spring unit according to claim 3 , comprising a fifth integrally formed spring portion, which fifth spring portion is arranged in use to be placed under compression during compression of the complex spring unit.
5. A complex spring unit according to claim 1 , wherein the second spring portion is continuous with the first spring portion.
6. A complex spring unit according to claim 2 , wherein the third spring portion is continuous with the second spring portion.
7. A complex spring unit according to claim 1 , wherein the second spring portion comprises a coiled tension spring.
8. A complex spring unit according to claim 1 , wherein, during compression of the complex spring unit, at least some of the spring portions become deformed at different stages to other spring portions.
9. A complex spring unit according to claim 2 , wherein the complex spring unit comprises the first, second and third spring portions and is arranged such that during compression of the complex spring unit the spring portions become elastically deformed according to the following phases:
a) a first phase including deformation of the second spring portion and
b) a second phase including deformation of the first spring portion.
10. A complex spring unit according to claim 9 , wherein the complex spring unit is arranged such that during compression the spring portions become deformed according to a third phase comprising solely or mainly of deformation of the first and third spring portions.
11. A complex spring unit according to claim 10 , wherein the complex spring unit is arranged such that during at least one phase of compression the second spring portion is relaxed.
12. A complex spring unit according to claim 4 , wherein the complex spring unit comprises first, second, third, fourth and fifth spring portions, and is arranged such that during compression of the complex spring unit the spring portions become elastically deformed according to the following phases:
a) a first phase comprising solely or mainly of deformation of the second and fourth spring portions; and
b) a second phase comprising solely or mainly of deformation of the first and fifth spring portions.
13. A complex spring unit according to claim 12 , wherein the complex spring unit is arranged such that, during compression the spring portions become deformed according to a third phase comprising solely or mainly of deformation of the first, third and fifth spring portions.
14. A complex spring unit according to claim 12 , wherein the deformation of the second and/or fourth spring portions comprises only extension under tension.
15. A complex spring unit according to claim 12 , wherein the complex spring unit is arranged within a sleeve or pocket.
16. A resilient pad or panel, cushion or mattress or upholstered unit, incorporating a complex spring unit according to claim 12 .
17. A resilient pad or panel according to claim 16 , wherein the pad or panel comprises a mattress, seat, seat back, mat or upholstered unit and compression of the pad or panel.